• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.12
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• pp.3079-3084
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• 2014

When an integrated circuit device is burned out under high-intense radiation and device-level simulation that usually requires manufacturer's proprietary information is not available, experimental conformation of a failure mechanism is often the only choice. To distinguish Latchup from other causes experimentally, a new combination of multiple techniques have been developed and demonstrated. Power supply circumvention, hot-spot monitoring using an infrared camera, and supply current monitoring techniques were implemented for the conformation of the Latchup.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.277-278
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• 2008

에너지절약에 대한 중요성과 관심으로 효율을 높이고 인버터 구동에 대한 서지내구성이 강화된 전동기용 절연소재의 개발에 관심이 커지고 있다. 최근 나노기술의 발달로 전동기용 에나멜 절연재에 나노입자를 강화하여 성능과 효율의 향상이 크게 개선되고 있다. 본 연구에서는 졸겔 제조법으로 PAI-MCS-A계 나노 하이브리드형 에나멜을 제조하여 기존 수지와의 전기적 특성을 비교 분석하였다. 강화입자로 선택한 나노 MCS 의 조성을 최대 30wt% 범위에서 메트릭스 수지와의 상안정성이 확인되었다. 특히 내아크성, 트래킹 시험에서 우수한 내구성이 나타났으며 이는 전동기용 에나멜 및 전력용 절연코팅용으로 사용이 기대된다. 전기적 절연, 섬락, 누설전류 등에 영향을 미치는 K, Na 값이 기존 다른 연구보고와 유사한 값을 가지고 있는 것을 확인하였다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.497-498
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• 2008

에너지절약에 대한 중요성과 관심으로 효율을 높이고 인버터 구동에 대한 서지내구성이 강화된 전동기용 절연소재의 개발에 관심이 커지고 있다. 최근 나노기술의 발달로 전동기용 에나멜 절연재에 나노입자를 강화하여 성능과 효율의 향상이 크게 개선되고 있다. 본 연구에서는 졸겔 제조법으로 PAI-MCS-A계 나노 하이브리드형 에나멜을 제조하여 기존 수지와의 전기적 특성을 비교 분석하였다. 강화입자로 선택한 나노 MCS의 조성을 최대 30wt% 범위에서 메트릭스 수지와의 상안정성이 확인되었다. 특히 내아크성, 트래킹 시험에서 우수한 내구성이 나타났으며 이는 전동기용 에나멜 및 전력용 절연코팅용으로 사용이 기대된다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.9
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• pp.718-726
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• 1998

J-E 특성 AC 임피더스 분석 그리고 주파수- 전도 특성들을 실험하여 임펄스 전류 서지가 ZnO 바리스터의 열화(degradation)에 미치는 영향을 고찰하였다. ZnO 바리스터 시편에 임펄스 전류(300A/$cm^24, 8/50$\mu s$)를 인가시킨 결과, 입계(grain boundary) 특성을 나타내는 비선형계수 $\alpha$와 E\ulcorner\ulcorner의 값은 크게 감소하였으나, 입자 특성을 나타내는 E_{100A}, E_{300A}$ 값에서는 큰 변화가 없었다. 이러한 열화 현상은 입계의 위치한 부성 전하 밀도, $N_s$의 감소에 한 쇼트키 장벽의 변화에 기인한 것으로 나타났다. 임펄스 서지에 의해 열화된 ZnO 바리스터는 AC 임피더스 분석에서 현저한 non-Debye 특성을 보이며, 이는 병렬 RC 네트워크로 모델링한 Cole-Cole 완화 관계식으로 입계의 열화 특성을 잘 설명할 수 있었다. 주파수-전도도 관계를 검토한 결과 Zno 바리스터는 호핑 전도(hopping conduction),\$sigma(\omega)\varpropto\omega^{\eta}$ 특성을 나타내면, 임펄스 서지가 인가된 이후 n 값이 감소하였다. 이는 임펄스 서지에 의해 입RP 결합 상태(defect states)가 호핑 전도가 발생하기 쉽고 다중(multiple)호핑에 의한 전도 메커니즘을 갖는 것으로 고찰되었다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.9
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• pp.842-850
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• 2003

The suspension insulators are subjected to harsh environments in service for a long time. The long-term reliability of tile insulators is required for both mechanical and electrical performances. This study describes some basic performance tests and accelerated aging test by cool-heat cycling methods and thermal mechanical performance test methods on alumina porcelain insulators (new and aged) used for transmission line in KOREA. There was no fail in electrical and mechanical performance tests such as a high voltage strength, a flashover voltage, and an impact strength in all samples. But in the case of accelerating aging tests which have above 9$0^{\circ}C$ temperature gradient, fracture phenomena was happened by a thermal shock in tile aged sample(sample A) with low alumina porcelain body. It was indicated that sample A was more severely aged than other samples. According to results of HRB test and microstructural analysis, it was reasoned that insulator bodies with the matrix reinforced with alumina crystalline phase have advantages over the suppression of crack advance. And cool-heat aging and mechanical thermal ageing tests shows that a temperature gradient is more effective to accelerating than a cycling number.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.32 no.3
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• pp.216-223
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• 2008

Reburning is a useful technology in reducing nitric oxide through injection of a secondary hydrocarbon fuel. In this paper, an experimental study has been conducted to evaluate the effect of fuel lean reburning on $NO_X/CO$ reduction in LPG flame. Experiments were performed in flames stabilized by a co-flow swirl burner, which was mounted at the bottom of the furnace. Tests were conducted using LPG gas as the reburn fuel as well as the main fuel. The effects of reburn fuel fraction and injection location of the reburn fuel were studied when the fuel lean reburning system was applied. The paper reports data on flue gas emissions and temperature distribution in the furnace for a wide range of experimental conditions. At steady state, temperature distribution and emission formation in the furnace have been measured and compared. This paper makes clear that in order to decrease both NOx and CO concentrations in the exhaust when the fuel lean reburning system was adapted, it is important that the control of some factors such as initial equivalence ratio, reburn fuel fraction and temperature of reburn fuel injection region. Also it shows the fuel lean reburning is also effective method to reduce NOx as much as reburning.

• Journal of Fisheries and Marine Sciences Education
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• v.27 no.3
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• pp.706-717
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• 2015

Marine casualties and environmental pollution have increased recently. Especially, the rate of incident of Coastal tankers is higher, but the assessment tool for safety management system is lack in this fields. However Oil Major Vetting System being professional assessment tool for tanker is widely applied in ocean going tanker by the worldwide Oil Majors. According to the analysis of the marine tankers' incidents which applied Oil Major Vetting System, the incidents were reduced rapidly for recent about 5 years. Using Oil Major Vetting System is helped to improve safety management and to prevent marine incidents. Therefore if applying a parts of the Oil Major Vetting Systems to the coastal tankers' Safety Management System, the Coastal tankers incidents would be reduced and improved gradually.

• Journal of Fisheries and Marine Sciences Education
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• v.27 no.3
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• pp.696-705
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• 2015

Approximately 4,000 vessels including sea trial ships per day are passing, entering or departing from Korea coastal waterway. Sea trial ships have erratic navigating patterns such as quick turning, crash stop and do not communicate with other vessels in appropriate time, so sea trial ships are often to expose dangerous situation such as collision in heavy traffic area. To identify the sea trial vessel's risk factors, this paper surveyed marine traffic volumes for 7 days in Korea harbour & coastal waterway, and it analyzed marine accident rate and intended to identify the risk degree of passing vessels. After that, this researched how many sea trial ship's traffic and what is the sea trial risk among sea trial items. We also conducted survey questionnaire and identified risk factors of sea trial ship. So this paper aimed to enhance the safety of korea coastal waterway to prevent sea trial ship's marine accident.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.23 no.8
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• pp.571-579
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• 2011

Heat pump systems for commercial building with variable refrigerant flow(VRF) are expanding a market due to high energy efficiency, lower maintenance cost and easy installation comparing with the conventional heat pump with the constant refrigerant flow. In general, heat pump systems degrade the energy efficiency in the extremely low temperature regions. In this study, VRF heat pump system with refrigerant heating is experimentally investigated to overcome the low heating performance in the extremely low temperature regions. VRF heat pump system with refrigerant heating is found out the sufficient heating performance in the -25 degree temperature condition comparing with the conventional heat pump system and is obtained more than 2,500 kPa high pressure in the evaporator at low temperature.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.23 no.8
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• pp.556-561
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• 2011

In this study, the theoretical maximum power of a heat engine was investigated by sequential Carnot cycle model, for a low-grade heat source of about $100^{\circ}C$. In contrast to conventional approaches, the pattern search algorithm was employed to optimize the two design variables to maximize power. Variations of the maximum power and the optimum values of design variables were investigated for a wide range of UA(overall heat transfer conductance) change. The results show that maximizing heat source utilization does not always maximize power.